1. Energy and Enzymes Chapter 6 Almost all energy for life is derived from the sun. Life requires energy.

2. Chemistry and Life Life is to a set of coordinated chemical reactions. – What determines what chemical reactions are possible?

3. Chemical Reactions Whether a chemical reaction will or won’t occur under particular conditions is determined by the laws of thermodynamics. 1 st Law of Thermodynamics– energy can neither be created nor destroyed only change form 2 nd Law of Thermodynamics– any change in energy causes the quantity of useful energy to decrease ( heat loss) ENTROPY– measure of randomness or disorder; all processes in an isolated system result in increase of disorder **NOTE living things are not in isolated systems ; use energy of sun to synthesize complex molecules

4. The Direction of Spontaneous Reactions (and what it takes to go the other way)

5. What determines if a reaction will occur? A + B --------- C if energy is available to do work after the reaction has occurred ( free energy) Exergonic rx’s– ones in which free energy is negative and energy is released Endergonic rx’s– products have more free energy than reactants and require an input of energy

6. Exergonic reaction

7. Endergonic reaction

8. ENERGY WITHIN LIVING THINGS 1)Energy- stored in chemical bonds between atoms and released when these bonds are broken. Some of this energy does work for the cell, some is given off as heat 2)Catabolism – the process by which molecules are broken down and their energy released ex: a) fermentation –breakdown of sugars in absense of oxygen b) respiration- breakdown of sugar in presence of oxygen

9. Breakdown of glucose (respiration)

10. Endergonic rx ( photosynthesis)

11. 3) metabolism – sum of all reactions that occur in a cell

12. ATP ( energy carrier molecule) 1) Structure– a) base= adenine b) sugar= ribose c) 3 phosphate groups

13. ATP USES 1) Chemical Work- needed to synthesize macromolecules

14. ATP USES 2) Transport work- needed to pump substances across cell membrane

15. ATP USES 3) Mechanical work- needed for muscle contraction ; chromosome movement

16. ATP – HOW IT PROVIDES ENERGY 1) Energy is released when ATP is hydrolyzed (broken down) to ADP. 2) ATP is restored from ADP and an input of energy. 3)ATP’s energy is used to drive endergonic (energy-requiring) reactions.

17. ATP PRODUCTION Chemiosmosis – production of ATP due to a hydrogen ion gradient across the plasma membrane

19. The “Nature of Life” – Coupling Favorable to Unfavorable Reactions Endergonic reaction + exergonic reaction Input of energy Energy is released

20. COUPLED REACTIONS ( REDOX ) oxidation –reduction reactions When electrons are transferred from one reactant to another. The loss of an electron from a substance is called oxidation. LOSS The gain of the electron is called Reduction. GAIN Ex: respiration, photosynthesis, fermentation

21. Photosynthesis 6CO2 + 6H20 + Energy-----C6H1206 + 6O2 Oxidation= loss of H+ atoms from water Reduction= gain of H+ atoms by Carbon dioxide Product = glucose forms Transfer of electrons occurs by a coenzyme NADP+

22. Respiration ( in mitochondria on animals) C6H12O6 + 6O2------6CO2 + 6H20 + Energy Oxidation= glucose transfer H+ Reduction= oxygen accepts H+ Occurs by coenzyme NAD+ by accepting electrons from H+ NAD+ + 2e- + H+ ------ NADH

23. COUPLING REACTIONS F. Coupling of exergonic and endergonic reactions (cont.) 1.. Energy carrier molecules (energy taxis) 2. ATP and electron carrier molecules

25. CARRIER MOLECULES

26. METABOLIC PATHWAYS --sum of all reactions that occur in a cell Metabolic pathway

27. Enzymes Speed Biochemical Reactions Enzymes are biological catalysts – substances that speed a reaction without being altered in the reaction. Most enzymes are proteins, some are RNA. BRING PARTICULAR MOLECULES TOGETHER AND CAUSE THEM TO REACT WITH ONE ANOTHER Model of the surface of an enzyme.

28. IV. Chemical reactions in living organisms need to be catalyzed A. Activation energy requirements for all the chemical reactions occurring in an organism are too high B. Catalysts reduce activation energy requirements

29. Activation without catalyst Activation energy with catalyst

30. Enzymes Lower a Reaction’s Activation Energy

31. Enzyme Action ACTIVE SITE= when substrate fits and forms a complex ; product released and enzyme free react again E + S ==== ES=== E + S

32. The Fit Between Enzyme and Substrate is Critical and Precise Hexokinase, an enzyme (blue), binding its substrate, glucose (yellow).

33. The active site of an enzyme is where substrate is bound. Many Enzymes Work by Altering the Shape of Their Substrates

34. Factors that affect enzyme speed 1) amount of substrate 2) temperature 3) pH

35. Coenzymes Assist enzymes Vitamins are part of coenzymes Vitamin deficiencies cause enzymatic reactions not to occur

36. Enzyme Deficiency and Health Most genetic disorders are due to a deficiency in enzyme function. This archival photo shows three children with the enzyme deficiency that causes phenylketonuria.

37. The synthesis of biological molecules often requires many enzyme-catalyzed steps. The entire set of steps is a metabolic pathway. Metabolic Pathways

38. The metabolic pathway that produces tryptophan – an amino acid. This is one of hundreds of metabolic pathways essential for life.

39. Enzyme Activity is Often Regulated Feedback inhibition - a common form of enzyme regulation in which the product inhibits the enzyme.

40. Other inhibition types 1) Competitive- a molecule close in shape to the substrate competes for the active site and reduces the concentration of available enzymes ex: pollutants, poisons 2) Noncompetitive– an inhibitor molecule binds to enzyme and alters shape of active site ; reduces enzyme function ex: penicillin disrupts enzymes necessary for bacteria to make their cell walls